It's a corruption of the Old French word 'cervelat' or modern French 'cervelas', both meaning a short, thick sausage. I guess, therefore, one would have to say 'France' in order to answer your question. The point is it is not a place-name.
I should, perhaps, have added above that the word 'savoy' - a type of cabbage - originated in Savoie, a region in south-east France. There just may, therefore, be some connection between 'sav...el...oy and that specific place-name, despite what I said earlier. The answer's still France, though!